A TALE OF TWO TRNAS: TRANSLATING THE SAME CODON DOES NOT IMPLY REDUNDANCY

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Murrill, Elizabeth

Abstract

A transfer RNA (tRNA) can form codon-anticodon interactions either by standard Watson-Crick base pairing or by forming a wobble base pair between the first position of the anticodon and the third position of the codon. This means that within the same isoaccepting tRNA group, one codon may be read by two individual tRNAs each interacting in one of the two ways. This leads to the question: Why would such redundancy occur? Through the inactivation of the gene that encodes for the threonine isoaccepting tRNA with the anticodon CGU (tRNA-CGU), it was found that the tRNA-CGU, which interacts with its cognate codon through Watson-Crick base pairing, is not essential for life in Escherichia coli. Yet, the tRNA-CGU is present in a majority of bacteria, leading one to expect that it must have a meaningful role in the process of translation that has caused it to either be a retained or a gained molecule for such bacteria. Evidence showed that the tRNA-CGU has specific properties that allow the tRNA to contribute more at increased temperatures to the translation of its codon, while the properties of the tRNAs that “wobble” to read the codon contribute less at increased temperatures. One possible, contributing property of the tRNA-CGU is the more stable codon-anticodon interaction formed by the standard Watson-Crick base pair. Since bacteria have to live in different environments and at various temperatures, such chemical stability may be key to the survival of these bacteria and why so many bacterial genomes have a tRNA that is seemingly redundant.

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